Plasmonic transducer having two metal elements with a gap disposed therebetween

ABSTRACT

An apparatus includes a waveguide configured to deliver light to a transducer region. The apparatus also includes a plasmonic transducer that has two metal elements configured as side-by-side plates on a substrate-parallel plane with a gap therebetween. The gap is disposed along the substrate-parallel plane and has an input end disposed proximate the transducer region and an output end. The transducer is configured to provide a surface plasmon-enhanced near-field radiation pattern proximate the output end in response to the light received by the waveguide.

CROSS REFERENCE TO RELATED CASES

This is a continuation of U.S. patent application Ser. No. 13/231,549,filed Sep. 13, 2011, now U.S. Pat. No. 8,451,705 which is herebyincorporated by reference in its entirety.

SUMMARY

Various embodiments described herein are generally directed to anear-field transducers that may be used, e.g., for heat assistedmagnetic recording. In one embodiment, an apparatus includes a waveguideconfigured to deliver light to a transducer region. The apparatus alsoincludes a plasmonic transducer that has two metal elements configuredas side-by-side plates on a substrate-parallel plane with a gaptherebetween. The gap is disposed along the substrate-parallel plane andhas an input end disposed proximate the transducer region and an outputend. The transducer is configured to provide a surface plasmon-enhancednear-field radiation pattern proximate the output end in response to thelight received by the waveguide. These and other features and aspects ofvarious embodiments may be understood in view of the following detaileddiscussion and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The discussion below makes reference to the following figures, whereinthe same reference number may be used to identify the similar/samecomponent in multiple figures.

FIGS. 1A and 2 are cross-sectional diagrams of an integrated opticalfocusing element and near-field transducer according to an exampleembodiment;

FIG. 1B is a perspective view of a near-field transducer according to anexample embodiment;

FIG. 3A is a graph showing simulation results of light absorbed instorage layer as a function of wavelength according to an exampleembodiment;

FIG. 3B is a graph showing simulation results of light absorbed in anear-field transducer as a function of wavelength according to anexample embodiment;

FIG. 4A is a graph illustrating an estimated distribution of electricfield strength in a recording media according to an example embodiment;

FIG. 4B is a graph illustrating estimated effect on absorption as afunction of waveguide length lapping tolerances;

FIG. 5A is a graph illustrating a calculated measure of efficiencyrelated to spacing between the light delivery components and near-fieldtransducer as shown in the example embodiments;

FIG. 5B is a graph illustrating isothermal contours near the magneticpole according to a thermal analysis of the example embodiments;

FIG. 6A is a graph showing the temperature rise versus down tracklocation for example embodiments under the same conditions as in FIG.5B;

FIG. 6B is a diagram showing the results of finite element thermalmodeling at the plane of the air bearing surface according to an exampleembodiment;

FIG. 7A is a perspective view of finite element thermal modeling resultsaccording to an example embodiment;

FIG. 7B is a perspective view of finite element thermal modeling resultsaccording to another example embodiment;

FIGS. 8A and 8B are perspective views of a waveguide near-fieldtransducers according to other example embodiments;

FIG. 9 is a process diagram illustrating a wafer process sequence thatcould be used in making a near-field transducer according to the variousembodiments;

FIGS. 10A and 10C are views on an air bearing surface plane ofnear-field transducers and recording poles according to additionalexample embodiments;

FIGS. 10B and 10D are cross sectional views of the near-fieldtransducers and recording poles shown in FIGS. 10A and 10C;

FIG. 11 is a perspective view of a waveguide near-field transduceraccording to another example embodiment;

FIGS. 12, 13A and 13B are graphs comparing absorption efficiency of thenear-field transducer of FIG. 11 and without rounded edges near the gapas a function of varying transducer length and width;

FIG. 14A is a graph illustrating dimension and arrangement of a channelwaveguide proximate a near-field transducer according to an exampleembodiment;

FIG. 14B is a field intensity plot of the waveguide and near-fieldtransducer arrangement shown in FIG. 14A;

FIGS. 15A-15F, 16A-16D, and 17A are cross-sectional diagrams of slidersections illustrating heat sinking features according to exampleembodiments;

FIGS. 17B and 17C are front views of plasmonic near field transducerelements according to additional example embodiments;

FIGS. 18A-18B are graphs illustrating analytical models used to predicttemperature profiles in a recording media according to embodiments; and

FIG. 18C is a graph comparing temperature profiles in a recordingmaterial based on the analytical models of FIGS. 18A and 18B.

DETAILED DESCRIPTION

The present disclosure relates to optical components used inapplications such as heat assisted magnetic recording (HAMR). A HAMRdevice utilizes a magnetic recording media (e.g., hard disk) that isable to overcome superparamagnetic effects that limit the areal datadensity of typical magnetic media. In order to record on this media, asmall portion of the media is locally heated while being written to by amagnetic write head. A coherent light source such as a laser may providethe energy to create these hot spots, and optical components, e.g.,built in to a slider that houses the write head, are configured directthis energy onto the media.

When applying light to a HAMR medium, the light is concentrated into asmall hotspot over the track where writing is taking place. In order tocreate this small hot spot, energy from a light source (such as a laserthat is integral to or separate from the write head) may be launchedinto a waveguide integrated into a hard drive head. The light propagatesthrough the waveguide and may be focused on to an optical near-fieldtransducer (NFT) by a focusing element. Example NFT transducers mayinclude a plasmonic optical antenna or a metallic aperture. Examplefocusing elements may include solid immersion lenses (SIL) and solidimmersion mirrors (SIM).

The NFT may be located at an air bearing surface (ABS) of a slider, andmay be placed in close proximity to a write head that is also part ofthe slider. This co-location of the NFT with the write head facilitatesheating the hot spot during write operations. The waveguide and NFT maybe formed as an integral part of the slider that houses the write head.Other optical elements, such as couplers, mirrors, prisms, etc., mayalso be formed integral to the slider. The optical elements used in HAMRrecording heads are generally referred to as integrated optics devices.

The field of integrated optics relates to the construction of opticsdevices on substrates, sometimes in combination with electroniccomponents, to produce functional systems or subsystems. For example, anintegrated optics device may transfer light between components viarectangular dielectric slab waveguides that are built up on a substrateusing layer deposition techniques. These waveguides may be formed as alayer of materials with appropriate relative refractive indices so thatlight propagates through the waveguide in a similar fashion as throughan optic fiber.

As a result of what is known as the diffraction limit, opticalcomponents cannot be used to focus light to a dimension that is lessthan about half the wavelength of the light. The lasers used in someHAMR designs produce light with wavelengths on the order of 800-900 nm,yet the desired hot spot is on the order of 50 nm or less. Thus thedesired hot spot size is well below half the wavelength of the light,and optical focusers cannot be used to obtain the desired hot spot size,due to diffraction. As a result, an NFT is employed to create thesehotspots on the media.

The NFT is a near-field optics device designed to reach local surfaceplasmon conditions at a designed wavelength. A waveguide and/or otheroptical element concentrates light on a transducer region (e.g., focalregion) near which the NFT is located. The NFT is designed to achievesurface plasmon resonance in response to this concentration of light. Atresonance, a high electric field surrounds the NFT due to the collectiveoscillations of electrons at the metal surface. Part of this field willtunnel into a storage medium and get absorbed, thereby raising thetemperature of a spot on the media as it being recorded.

In reference now to FIGS. 1A and 2, cross-sectional diagrams illustratesan integrated optical focusing element according to an exampleembodiment. As shown in FIG. 1A, this embodiment includes waveguide core101 that directs light rays 106 to a planar SIM (PSIM), here indicatedby way of SIM sidewall 102. The waveguide core 101 may be formed fromany material that has a higher index of refraction than cladding (e.g.,see waveguide cladding layers 206, 208 in FIG. 2). For example, thewaveguide core 101 may be made from Ta₂O₅, TiO₂, ZnS, SiN, and thecladding 206, 208 may be made from Al₂O₃, SiO₂, Y₂O₃, Hf₂O₃, MgF₂, MgO₂,SiON_(x), AlN. The cladding layers 206, 208 may each be made of adifferent material. The core 101 and cladding layers 206, 208 maygenerally be part of a light delivery system that receives light from asource (e.g., laser diode) and directs it to the SIM 102. These andother components may be built on a common substrate (not shown) usingwafer manufacturing techniques known in the art.

The SIM 102 may be formed as a parabolic cutout of surroundingdielectric waveguide material 104 (e.g., Al₂O₃, SiO₂, SiOxNy, MgO, HfO₂,Y₂O₃, Ta₂O₅, TiOx). The cutout may be formed from/coated with areflective material (e.g., Au, Al), so that light rays 106 entering thePSIM 102 by way of waveguide core 101 are focused to a focal region 108.The focal region 108 is proximate an air bearing surface 110, and thefocused light 106 is directed out of the air bearing surface 110 (in thepositive y-direction as seen in FIG. 1) to be absorbed by storage media(not shown). While the embodiments described below may be describedbeing used with a focusing element such as a SIM or SIL, otherembodiments may not require these elements, or may use differentelements. For example, incident waves could be launched onto the NFTdirectly from a waveguide, e.g., a channel or planar waveguide.

An NFT is a transducer that can be made of any known plasmonic material(e.g., Au, Ag, Cu) and may be positioned at or near the focal region 108to further direct the energy to the air-bearing surface 110 (ABS). Insome configurations, the NFT may be may be configured as a single pieceof plasmonic material shaped like a tapered pin or circular disk with apeg attached (e.g., shaped like a lollipop). Such an NFT design(hereinafter referred to as a “one-piece NFT”) may have one end disposednear the focal region 108 and extend downwards (in the positivey-direction) to the ABS 110. Electric fields are excited on the surfaceof the NFT, and these fields are directed out to the air bearing surface110 for delivery to the media. A magnetic pole (e.g., pole 202 in FIG.2) is positioned proximate the NFT (e.g., above or below the NFT in thez-direction) and applies magnetic fields to the heated media (e.g.,media 204 in FIG. 2) during recording. The recording pole 202 may beconfigured for perpendicular recording.

An analysis was performed for a one piece NFT configuration that wasoptimized for light wavelength λ=830 nm. This design was a disk-pegconfiguration, with disk diameter of 200 nm, thickness 30 nm (along thez-direction), and the protruded peg length 15 nm (along they-direction). At resonance, over 10% of the applied optical energy isabsorbed by this one-piece NFT. This resulted in raising the NFT to highenough temperatures that component damage could result. A similar resultwould be expected for other one-piece NFT designs, e.g., a straight ortapered elongated peg.

In order to alleviate negative effects of high temperatures, a one-pieceNFT can be thermally coupled to the magnetic pole via a heat sink. Aheat sink may prevent failure of the one piece NFT due to overheatingunder some conditions. Even with the heat sink, however, temperaturesinduced during recording in a one-piece NFT of may be high enough tocause material diffusion between the NFT, pole, and heat sink. Thisreduces NFT efficiency and also reduces the magnetic moment of therecording pole.

Another effect that may be seen with a one-piece NFT involves thegeneration of side-lobes that could cause unintended recording/erasureoutside the hotspot. A one-piece NFT with non-smooth outer contours(e.g., disk/peg configuration) is excited by a longitudinally polarizedoptical spot with the electrical field along the y-direction. On eitherside of this optical spot there may be another optical spot that ispolarized transversely, e.g., with the electric field along thex-direction. The peak-to-peak spacing between the two transverselypolarized optical spots in the analyzed case was estimated asapproximately 350 nm at wavelength λ=830 nm. These fields will becoupled into the storage media, resulting in potential side-loberecording/erasure. Attempts to block the two side-lobes may eventuallydecrease the NFT efficiency and raise the local temperature of thedevice.

As a result of the above, an alternate NFT design 114 is shown in FIGS.1A, 1B, and 2. This alternate NFT 114 includes a ridge waveguide core118 (also referred to herein as a “ridge waveguide,” “gap,” and/or“notch”) with plasmonic metal cladding. The cladding may be formed oftwo metal elements 116 that are generally plate or bar shaped, andarranged side-by-side on a common plane (e.g., xy-plane which may beparallel to plane of the wafer substrate) with the gap 118 therebetween(see FIG. 1B). The gap 118 has a wider bottom opening dimension 120(W_(b)) than at the top 122 (W). The narrower top opening 122 may beplaced in proximity to a recording head.

As seen in FIG. 1A, the PSIM 102 focuses a transverse electric (TE)polarized light into an input end of the ridge waveguide 118. In thisillustration, the NFT 114 is shown disposed above the bottom of the SIM102, with the input end separated from the focal region 108 by distance121. It will be appreciated that distance 121 may be negative, that isthe focal region may be situated inside the NFT 114 in someconfigurations. In other configurations, the input end of the NFT 114may be placed below the SIM 102, e.g., extending further down beyond thefocal region 108 (in the positive y-direction). Similarly, while theoutput end of the NFT 114 is shown extending flush with the ABS 110, thewaveguide core 118 (and/or metal elements 116) may be terminated abovethe ABS to improve coupling efficiencies.

The metal cladding elements 116 provide a surface plasmon-enhancednear-field radiation pattern proximate the output end in response to thelight received by the SIM 102. Light waves propagating through the ridgewaveguide 118 bend upward toward the narrow gap 122, which has a highereffective refractive index than the bottom gap 120. Localsurface-plasmon resonance may be reached by tuning the bottom open widthW_(b) 120, height 132, and the overall width 130 at a desired excitationwavelength. The waveguide length 124 (L) can be optimized at Fabry-Perotresonance. Resonance and light focusing capability of this configuration114 result in large amount of optical energy condensed inside the gap118 and out of the air-bearing surface 110, where it is then coupledinto a storage medium for heat assisted recording.

The NFT 114 can be self heat-sinked due to its relatively large width130 along the x-direction. This allows an oxide dielectric material tobe placed between the NFT 114 and magnetic recording pole, therebypreventing diffusion between the NFT 114 and pole material. This NFT 114configuration may also be usable to achieve small optical spots inrecording media with no plasmonic layer. Direct coupling from the PSIMfocusing to a data storage medium is minimal due to the small ridgecross section, large width 130, and length 124. This design 114 canreduce or eliminate PSIM side-lobe recording or erasure.

This NFT design 114 may also have useful thermo-mechanical properties.With one-piece NFT designs, substantial amounts of energy may beconverted into heat within an elongated portion proximate the ABS 110.Due to relatively small dimensions of the elongated portion, energydensity at this portion of the one-piece NFT can be an order ofmagnitude higher then it is elsewhere in the NFT, resulting insignificant localized heating. Other heated components in the head(coils, heaters, etc.) may employ the ABS 110 as a heat sink, but only asmall surface area of a one-piece NFT may expose to the ABS 110 (e.g.,in configurations where the NFT is surrounded with a dielectric such asAl₂O₃). One way to remove excess heat from a one-piece NFT design is toconnect the NFT to the recording pole tip through a heat sink (e.g., agold-cylinder). However, the pole tip may also be of a reduced size toaccommodate a smaller magnetic footprint, and this may result in thepole tip being heated up excessively. If the pole tip is heated enough,this will lower a thermal gradient between pole tip and NFT, and makethe heat sinking less effective.

The waveguide NFT design 114 can be designed to minimize such thermalissues. In the waveguide NFT 114, there are no relatively small featuresthat make it difficult for thermal energy to dissipate. In some thermalmodeling (shown in detail below) most of the energy was found to beabsorbed in vicinity of the sharp gold corner at the ABS surface, withenergy density being at the similar level to energy density beingabsorbed in the one-piece NFT. Temperature elevation at this corner isreduced, due in part to the output end of the cladding portions 116being directly exposed to the ABS 110, and also due to the claddingportions including relatively large areas of highly thermally conductivematerial (e.g., gold).

For example, in one configuration, the surface area of a one-piece NFTexposed to the ABS 110 is approximately 900 nm². In a similar context,the area of the waveguide NFT 114 that would be exposed to ABS 110 is190,000 nm², at least two orders of magnitude higher. Ballistictransport of heat away from at ABS 110 is directly proportional to theavailable surface area. Thus the waveguide NFT design 114 can takeadvantage of significantly increased heat sinking from the ABS 110.

To demonstrate the performance of NFT design 114, an example structurewas numerically modeled to determine optical, near-field, andthermo-mechanical performance. The NFT 114 was modeled to select optimumvalues of the bottom width W_(b) 120 and length 124, with the top gapwidth 122 and top gap height 126 both being set at 30 nm. The angle 128was set to 30 degrees, and the total length of the two metal pieces plusthe gap along the x-direction (dimension 130) was 630 nm. For thefollowing simulations, the ridge bottom width dimension 120 (W_(b)) wasset as 100 nm, and length 124 was set as 280 nm. The total metalthickness 132 (H) was set as 150 nm. These dimensions are purely forpurposes of illustration. For example, it is expected that the top gapheight could be smaller or zero, effectively forming a sharp corneralong the upper edge of the gap 118.

In FIG. 3A, a graph 300 shows the light absorbed in a FePtCuC storagelayer resulting from the simulation. The light was absorbed in a volumeof 50 nm×50 nm times the storage layer thickness. This illustrates thatthe NFT 114 of this configuration is suitable for use with wavelengthsbetween 870 to 900 nm. Seen in graph 302 of FIG. 3B is a plot indicatingthe light absorbed in the NFT a function of excitation wavelength. Inthis modeling it was assumed that the planar waveguide is a 150-nm thickTa₂O₅ core with index of refraction n=2.09, cladded by Al₂O₃ of n=1.65.The ridge NFT core 118 was also Al₂O₃ and cladded by gold metal (metalcladding elements 116). The storage medium was modeled as a 12.6-nmthick FePtCuC magnetic layer of n=2.54+j 1.527 and a 20 nm thick MgOlayer of n=1.7 on a silicon substrate. The head-medium spacing (HMS) wasset as 8 nm with effective index of refraction n=1.2116. The PSIM 102was modeled as 50 μm wide at the top opening and 100 μm long (in they-direction). The incident beam was TE mode normal to the waveguideplane (xy-plane) and Gaussian parallel to the waveguide plane with 1/e²intensity radius 24 μm. The total optical power flowing onto the PSIM102 is 1 watt.

As shown in graph 300, the coupling efficiency (CE) in this simulationexhibits resonance, which peaks at λ=890 nm. The 90% CE range is 58 nmin wavelength wide. The light absorption of the media as seen in graph300 peaks below the absorption in NFT seen in graph 302, the latterbeing 12% at the peak resonance CE wavelength of λ=890 nm. In someapplications, it may be desirable to use a longer wavelength, forinstance, λ=980 nm, to reduce dissipation in the NFT.

In reference now to FIG. 4A, a graph 400 illustrates an estimateddistribution of electric field strength (E²) in the media at 2 nm belowthe storage layer for light having wavelength λ=910 nm. The displayedelectric field has been multiplied by λ. The spacing 121 between the NFT116 and the focal point 108 is 40 nm long and filled with Al₂O₃. Themaximum field strength of region 402 is between 13000 and 14800 volt²and field strength in the outer region 404 is between 5870 and 9460. Itcan be seen from graph 400 that the electric field strength E² in themedium generally has a teardrop shape, and the E² profile bends inwardat region 406 from the top of the gap, where a magnetic pole will beplaced. This field profile will yield a flat thermal profile, which canprovide a smaller effective thermal hotspot for writing straightmagnetic transitions. Modeling also shows that if the head-mediumspacing decreases to 5 nm, this inward field profile 406 is even morepronounced. The full-width-at-half-maximum (FWHM) optical spot at themiddle of the storage layer is 42 nm along the x-direction (cross track)and 62 nm along the z-direction (down track) for the 30 nm gap at the 8nm head-medium spacing.

Another consideration in NFT design relates to lapping tolerance.Lapping tolerance refers to dimensional tolerances of the lappingprocess used to bring the integrated optical components to finaldimension. In FIG. 4B, a graph 410 shows the estimated effect ofwaveguide length lapping tolerances on absorption at the media(wavelength λ=910 nm). This example assumes a nominal waveguide length124 of 280 nm. As with FIG. 3A, the absorption refers to light absorbedin a FePtCuC storage layer in a volume of 50 nm×50 nm times the storagelayer thickness. The resulting curve represents a variation in theabsorption versus ridge waveguide length due to lapping tolerance. At90% CE, the lapping tolerance is approximately 30 nm, which is reachableusing current processes.

In reference now to FIG. 5A, a graph 500 shows a calculated measure ofNFT efficiency related to spacing between the light delivery components(e.g., waveguide, SIM) and NFT as shown in the example embodiments. Inthis example, the absorption (measured similarly to the absorptiondescribed in FIGS. 3A and 4B) is calculated based on varying the spacing121 (L₁) between the focal point 108 in the planar waveguide core 101and the ridge waveguide of the NFT. This graph 500 shows that the NFTefficiency increases by approximately 20% at spacing L₁=20 nm and ispeaked at L₁=30 nm. At L₁=60 nm, the CE is only slightly decreased fromits peak value.

To demonstrate the NFT performance for magnetic recording, a Fe₅₅Co₄₅magnetic was modeled as being placed near the NFT (e.g., see pole 202 inFIG. 2). The simulation uses a staircase pole, with 15 nm step every 20nm. The NFT-pole distance is 15 nm near the air-bearing surface 110. Forthis modeling, it is assumed the media 204 has an Fe storage layer. Thepresence of the FeCo pole decreases the NFT efficiency by 30%. Inreference now to FIG. 5B, a graph 502 shows isothermal contours near themagnetic pole according to example embodiments. The isothermal contoursin graph 502 represent respective temperature rise of 1000, 1500, 2000,and 2500 K in response to 1 ns of irradiation at 100 mW. In FIG. 6A, agraph 600 shows the temperature rise versus down track location (in thez-direction) at x=0 under the same conditions as FIG. 5B. These graphs502, 600 demonstrate that a low curved thermal contour can be obtainednear the pole for magnetic recording, with the maximum thermal gradientbeing about 5 nm away from the pole. If the head-media spacing drops to5 ns, the isothermal contour is almost flat near the pole, which rendersa sharp magnetic transition.

A finite element, thermo-mechanical analysis was performed to calculatemaximum temperature in this NFT design, the NFT being designated here byreference numeral 114A. A result of this modeling at the plane of theABS is shown in FIG. 6B, and a perspective view, close up is seen inFIG. 7A. As shown in FIG. 7A, the NFT 114A uses modified gold claddingelements 116A with extensions 702 that reach up near to the recordingpole 202 so that the pole 202 provides some level of heat sinking Thepole is 300 nm wide and the NFT is 630-nm wide (measured along thex-direction as seen in FIG. 1B). The portions 116A were modeled as gold.While published values of thermal conductivity for gold are around 318W/mK, it has been found that the thermal conductivity of thin gold filmsdecrease with decreasing film thicknesses. Thermal conductivity for theportions 116A was estimated as 110 W/mK.

As can be seen in FIG. 7A, the maximum temperature is reached at the ABSsurface at the corners 704 of the NFT 114A that correspond to the narrowportions of gap 118. The steady-state temperature elevation over ambientat the maximum temperature point is 7.4 K. A similar finite elementanalysis was performed for a one-piece configuration under the sameloading conditions (same air-bearing design, same disk rotational speed,same amount of incident power, etc.). In that case, the maximumtemperature was reached at the NFT where it meets the ABS, and thetemperature elevation was 14.9 K for NFT thermal conductivity of 110W/mK, which is about twice the temperature elevation of the waveguideNFT.

Because the thickness of the waveguide NFT is about five or more timesthat of the one-piece NFT, the effective thermal conductivity of thegold will change between the two designs. In the case of the current NFT114A, thermal conductivity is around 110 W/mK, compared to 50 W/mKestimated for 50 nm thin film, or even 30 W/mK, estimated for 25 nm thinfilm, either of which could be the case for a one-piece NFT. Another setof analysis was run for one-piece NFT using thermal conductivities of 50W/mK, and 30 W/mK, which resulted in temperature elevation of 21.9K, and29.2K, respectively. In contrast, using similar reduced thermalconductivities for the configuration 114A shown in FIG. 7A showedtemperature elevation of 33% and 25%, respectively, when compared to thesame values applied to the one piece NFT.

Another finite element thermal analysis was performed using the NFTconfiguration 114 seen in FIG. 7B. In this configuration, the goldportions 116 are of a geometry similar to that shown in FIG. 1B. As inFIG. 7A, the pole is 300 nm wide and the NFT is 630 nm wide. Theseparation of the gold portions 116 from the recording pole 202 (e.g.,via dielectric material) results in there being reduced heat sinkingprovided by the pole 202. The maximum temperature elevation in thisexample is 8.9 K at regions 706 using effective NFT thermal conductivityof 110 W/mK. While this temperature elevation is slightly higher thanthe 7.4 K seen in the heat sinked version of FIG. 7A, this showsnonetheless that cooling through the ABS surface dominates in this typeof NFT configuration 114, 114A.

In general, it is estimated that out of 1 mW of incident power deliveredto these different NFT configurations, 20.38% is converted into heat fora one-piece NFT and 17.9% is converted into heat for the current design114, 114A. Therefore this latter configuration 114, 114A provides arobust thermo-mechanical solution to delivering energy to a recordingmedia. Configuration 114, 114A should operate with relatively lowmaximum temperature, and reduce heating of the recording pole tip.

In reference now to FIG. 8A, a perspective view illustrates a waveguideNFT configuration 802 according to another example embodiment. As withthe previous configuration, the NFT 802 includes metal elements 804 thatsurround a dielectric gap 806. The metal elements 804 may be made of aplasmonic material, e.g., gold, silver. At a first end 808 of the NFT802 (e.g., output end that faces the ABS) the core gap 806 includes anarrow portion 810 that transitions to a wider portion 812 at angle 814.At the opposite end 816 of the waveguide 802 (e.g., end that faces theSIM and/or light delivery waveguide), the narrow portion 810 from end808 has tapered out to wider dimension 818. In this example, the gap 806includes a first portion 806A near the ABS with substantially parallelsides, and a tapered portion 806B. In the illustrated NFT 802, the widerportion 812 tapers linearly from first end 808 to second end 816,however this two-stage profile could be similarly applied to otherfeatures of the core geometry, including the wider portion 812. Thechange in the gap along the y-direction in the tapered sections could beany linear or nonlinear profile. This configuration 802 may improve theimpedance match and exhibit improved efficiency under some conditions.

In reference now to FIG. 8B, a perspective view illustrates a NFTconfiguration 822 according to another example embodiment. Thisconfiguration includes metallic elements 824, 826 on either side of acore 828 (e.g., dielectric core). The core 828 includes a wider portion830 and a narrower slot 832. Light is evanescent through the slots 830,832. The metallic elements 824, 828 may be formed as a homogenousmaterial, or could be made from different materials. Efficiency may beimproved if, for example, the top portions 824 are formed from Au andthe bottom portion is formed from Cu. As with the configuration 802 inFIG. 8A, the core 828 in configuration 822 could be tapered in they-direction.

In reference now to FIG. 9, a process diagram illustrates an examplewafer process sequence that could be used in making a waveguide NFT suchas is shown in FIGS. 1B, 8A, and 8B. Referring first to stage 900, twolayers 902, 904 of waveguide dielectric material (e.g., Al₂O₃, SiO₂) areoverlaid with a hardmask (e.g. tantalum/amorphous carbon) 906. Thelayers 902, 904 may be laid on top of other layers (not shown) that areultimately built up from a common, substantially planar substrate (e.g.,the substrate being planar within manufacturing tolerances associatedwith the relevant processes). The hardmask materials are used as aninductively coupled plasma (ICP) etch hardmask and chemical-mechanicalplanarization/polishing (CMP) stop layer. A photoresist 908 is placedover the hardmask 906 to define a first (e.g., narrow) portion gap(e.g., gap 122 in FIG. 1B) of the NFT waveguide core. The photo resist908 is elongated (e.g., a line) in a direction perpendicular to thepage. The photoresist 908 determines the width of the narrow portion ofthe gap, while the thickness of the hardmask 906 defines the height ofthe narrow portion of gap (e.g., dimension 126 in FIG. 1B).

At stage 909, the line pattern defined by the photoresist 908 has beentransferred to the hardmask layers 906 by either mill, etch or both. Thephoto resist 908 is stripped after the etch. At stage 910, an ICP etchhas been used to etch into layer 902 with the desired wall angle and toa target depth (dimension 132 minus dimension 126 in FIG. 1B). Theremaining portion of the layer 902 forms a second portion of the gap. Atstage 912, an Au film 914 is filled in to cover the etch-out area bysputter deposition and/or by plating. At stage 916, the wafer beenplanarized and stopped on the hardmask layer 906. At stage 918, thehardmask layer 906 has been removed by etch, which is selective to thedielectric material in the field and to the Au film. At stage 920, thevoid left by the removed hardmask layer 906 has been backfilled withwaveguide dielectric film 922 and buffed in order to give goodstep-height coverage over the Au geometry if necessary.

An alternative design and corresponding process would involve formingthe sloped wall by using the sloped wall process described above,letting the wall cut right down through the NFT, and then depositing adielectric to form the NFT-to-pole spacing. If the dielectric isconfined to near the gap, this would also allow the NFT to connectdirectly to the pole outside the gap region and allow the pole to act asa heat sink for the NFT. The material properties can be chosen to give agood coupling efficiency and to reduce the coupling to the pole, sinceit wouldn't need to be a low loss material (low k), since it isn't partof the waveguide.

In reference now to FIGS. 10A-10D, additional configurations of an NFTand associated recording poles are shown. FIGS. 10A and 10C representviews of respective waveguide NFTs 1002, 1004 and recording poles 1006,1008 on an ABS plane. Waveguide NFT 1002 may be configured similar tothose shown in FIGS. 1B and/or 8A, and NFT 1004 may be configured asshown in FIG. 8B. In FIGS. 10B and 10D, cross sectional views representyz-plane cross sections near respective air bearing surfaces 1014, 1016that may be applicable to both NFT configurations shown in FIGS. 10A and10C.

As seen in FIGS. 10B and 10D, the recording poles 1006 may take onalternate geometries near the air-bearing surface. Because the surfaceof the NFTs 1002, 1004 adjacent the poles 1006, 1008 are flat, thewriter can employ features to achieve a large field with fast rise time.Optical delivery components 1010, 1012 (e.g., SIMs, waveguides) are alsoshown positioned adjacent to the NFTs 1002, 1004.

In reference now to FIG. 11, a perspective view illustrates a waveguideNFT configuration 1102 according to another example embodiment. As withthe previous configuration, the NFT 1102 includes metal elements 1104that surround a dielectric gap 1106. The metal elements 1104 may be madeof a plasmonic material, e.g., gold, silver. At a first end 1108 of theNFT 1102 (e.g., output end that faces the ABS) the gap 1106 includes anarrow portion 1110 that transitions to a wider portion 1112 (bottom gapwidth W_(b)) at angle 1114.

At the opposite end 1116 of the waveguide 1102 (e.g., end that faces theSIM and/or light delivery waveguide), the corners of the metal elements1104 near the gap 1106 are tapered using rounded edges. Radiuses 1118taper the narrow portion 1110 of the gap, and radiuses 1120 taper thewider portion 1112 of the gap 1106. While the rounded edges 1118, 1120may be described and modeled as circular radiuses herein, it will beappreciated that the rounded edges 1118, 1120 may conform to any smoothprofile, such as parabolic, logarithmic, exponential, etc. Further,similar rounded edges may be applied elsewhere to the NFT 1102, such asedges near input end 116 facing away from the gap 1106. The NFT 1102 maybe formed using previously described processes, e.g., as shown in FIG.9.

This configuration 1102 with tapers 1118, 1120 may exhibit improvedimpedance matching with optical delivery components (e.g., SIM and/orwaveguide). For example, if large light reflection occurs at theentrance end 1116 of the NFT 102, less energy is delivered via theplasmonic elements 1104, reducing NFT efficiency. The rounded corners1118, 1120 are one feature that may help improve impedance matching,thereby helping to increase optical power delivery efficiency.

To reduce impedance mismatches, the rounded edges 1118, 1120 result inthe gap 1106 having a smoothly tapered profile along light propagationdirection (y-direction). Due to this taper, the effective mode index ofthe NFT gradually increases, which reduces the light reflection at theNFT entrance. Moreover, as distance from the input end 1116 increases,the NFT waveguide mode index increases, which focuses the incident beamlaterally into the gap 1106. The straight shape of the gap following therounded edges 1118, 1120 afterward helps ensure that the optical spotsize across the gap 1106 does not change.

To demonstrate the performance of this NFT design 1102, the dimensionsare optimized by varying the bottom gap width 1112 (W_(b)) and the ridgewaveguide length 1122, with light wavelength λ set to 830 nm, top gap1110 size set to 20 nm, and gap angle 1114 set to 30°. Also in thismodeling, the thickness 1124 of the top gap was set to 0 and total NFTwidth 1126 (W₁) was set to 680 nm. The NFT height 1128 was also set to afixed value of 448 nm. A first set of results (shown in FIGS. 12A and12B) was obtained for the configuration 1102 without the rounded edges1118, 1120, and then a second set of results (in FIGS. 13A and 13B) wasobtained with the rounded edges 1118, 1120.

Light was modeled as being delivered to the NFT 1102 by a planarwaveguide (e.g., waveguide 101 in FIGS. 1A and 2) having a 150-nm thickTa2O5 core of index of refraction n=2.09, and cladded by Al₂O₃ ofn=1.65. The NFT core in gap 1106 was also Al₂O₃ and cladded by elements1104 formed of gold metal. The PSIM (e.g., PSIM 102 in FIG. 1A) wasmodeled as 50-μm wide at the top opening and 100-μm long. Normal to thewaveguide plane, the incident beam on the PSIM is a fundamental TE mode;parallel to the waveguide plane it is Gaussian with 1/e² intensityradius of 24 μm. The total optical power flowing onto the PSIM is 1watt. The storage media was modeled as a 12.6-nm thick FePtCuC magneticlayer of n=2.54+j 1.527 and a 20-nm thick MgO layer of n=1.7 on asilicon substrate. The head-medium spacing (HMS) is 8-nm with effectiveindex of refraction n=1.2116.

In FIG. 12, curve 1202 shows the computed light absorption efficiency ina 50 nm by 50 nm footprint of a media storage layer as a function of NFTlength 1122, with the bottom gap width 1112 (W_(b)) set to 260 nm andNFT height 1128 set to 448 nm. In this curve 1202, there were no roundededges 1118, 1120 at input end 1116 of the NFT 1102. To see thedifferences in efficiency due to the rounded edges 1118, 1120, a secondmodel included quarter-circled shapes at the NFT entrance with radius ofcurvature R=150 nm. The results of this simulation are represented inFIG. 12 by curve 1204, which shows the media absorption efficiency as afunction of NFT length 1122 (NFT width of 680 nm is the locallyoptimized size for the results of curve 1204).

In FIG. 13A, a graph shows a similar light absorption efficiency asdescribed in relation to FIG. 12, except that efficiency is presented afunction of bottom gap width 1112 (W_(b)) for an NFT without roundededges 1118, 1120. For this graph, NFT width 1126 (W₁) of 680 nm is used,and NFT lengths 1122 (L) are set to 85 nm and 215 mm. It can be seenthat two modes appear at L<300 nm. The optical efficiency of the firstmode, at NFT length of 85 nm, peaks at a bottom gap width of 260 nm,while the second mode, at NFT length of 215 nm, peaks at a bottom gapwidth of 180 nm. The highest efficiency seen here is around 0.032.

In FIG. 13B, a graph show the efficiency as a function of NFT overallwidth 1126 (W₁) for two peak NFT lengths (190 nm and 310 nm,respectively) for an NFT with rounded edges 1118 and a bottom gap width1112 (W_(b)) of 260 nm. It is evident that two modes are also observedat NFT lengths 1122 (L) of 190 nm and 310 nm, respectively. Theefficiency of the first mode seen in FIG. 13B is increased to 0.052 atan optimal width 1126 of around 760 nm. While FIGS. 13A and 13B showefficiency as a function of different geometric features (W_(b) versusW₁), the graphs generally illustrate an increase in efficiency usingrounded edges 1118, 1120. Greater efficiencies may be possible basedupon further optimization analyses. Such optimizations may involvevarying, for example, dimensions 1112, 1122, and 1126 and a shape of therounded edges 1118, 1120 for a desired wavelength.

The results described above assumed light delivery via a planarwaveguide and SIM. Other delivery mechanisms are contemplated forexciting the NFT according to any of the previously describedconfigurations. For example, an NFT could also be excited by adielectric channel waveguide. An example of a channel waveguidearrangement is seen in the graph 1402 of FIG. 14A, which showsdimensions and arrangement of components in an xy-plane (using ananalogous coordinate system as in previous examples). The graph 1402shows an NFT 1404 with a rounded, tapered input end at and input portionof a gap 1405, similar to that shown in FIG. 11. The NFT 1404 in thisexample is rounded both near and away from the gap. One end of a channelwaveguide 1406 is proximate the input end of the NFT 1404. An output endof the NFT 1404 is proximate a media surface 1406.

The geometry of the NFT 1404 is similar to what has been describedearlier. The cross-section for the channel waveguide 1406 used in thismodeling is 475 nm (cross-track)×285 mm (down-track). These parametersare merely representative, they are not intended to be limiting. Thecore of the waveguide was modeled as Tantalum, although this materialchoice is not intended to be limiting either. The computed electricfield intensity for the geometry of FIG. 14A is shown in FIG. 14B.Generally, the field intensity is in the range of 10^(2.4) to 10^(3.2)in region 1410 along the gap of the NFT 1404, where it reaches a peak ofabout 10⁴ proximate the surface of the media 1406 at regions 1412.

The regions of high field intensity seen in FIG. 14B may also begenerally indicative of regions of high temperature, as some of thelight is absorbed in the NFT 1404 due to the Joule effect. Thistemperature increase can also be seen in the thermal modeling resultsshown in FIGS. 7A-7B, which shows highest temperatures near the NFT gap.As described above, a portion of the NFT exposed to the ABS candissipate heat generated in the NFT. In the discussion that follows,additional heat dissipation methods/structures are described that canfurther assist in heat dissipation and with minimal penalty to (orpossibly enhancement of) NFT efficiency.

In embodiments shown in FIGS. 15A-15F and 16A-16D, a separate heat sinkmay be used to assist drawing heat away from an NFT 1500, either aloneor in combination with a recording pole. These may have enough thermalmass to dissipate heat away from the NFT (e.g., away from the ABS) toreduce peak temperatures at the NFT gap. The heat sink and/or recordingpoles may also be able to dissipate heat (e.g., via convection) at theABS. Generally, a material (e.g., dielectric) that fills the NFT gap mayalso be chosen to have high thermal conductivity and/or low thermalinterface resistance where this material interfaces with the NFTelements, heat sink, and/or recording poles. A spacer material betweenheat sink and pole might be used to prevent pole corrosion.

In FIG. 15A, a cross-sectional diagram illustrates an example of heatsinking features proximate NFT elements 1500 at a plane parallel to theABS according to an example embodiment. For convenience, the samereference numeral will be used to refer generally to an NFT in FIGS.15A-15F, 16A-16D, which illustrate heat sink configurations according toexample embodiments. The NFT 1500 in FIGS. 15A-15D and 16A-16D mayinclude any features and/or geometry previously shown and described,e.g., in FIGS. 1A-1B, 7A-7B, 8A-8B, and 11. The diagrams of FIGS.15A-15D and 16A-16D use the same reference axis as shown in FIGS. 15Aand 16A.

The NFT 1500 in FIG. 15A is proximate a recording pole 1504A, which maytaper/slant towards the NFT 1500 near the ABS such as shown in, e.g.,FIGS. 2, 10B, and 10D. This can be done by letting the sloped pole cutdown through the NFT (e.g., intersecting with the NFT) and only puttinga dielectric material in the NFT-pole spacer near the gap (seediscussion of FIG. 17 below). A heat sink 1502A includes portionsproximate the NFT on either side of the recording pole 1504A. In FIG.15B, an alternative arrangement includes heat sink 1502B between the NFT1500 and recording pole 1504B. The configuration of the heat sink 1502Ballows pole tip 1504B to be wider (in the cross track direction) thanpole tip 1504A. To reduce impact on NFT efficiency, the length of theheat sinks 1502A, 1502B in the x-direction can be optimized to yielddesirable NFT characteristics. In one implementation, 1502A was around400 nm wider than NFT 1500 along x-direction, and NFT efficiencyimproved by 35%.

Another option is shown in FIGS. 15C and 15D, which show analogousconfigurations to FIGS. 15A and 15B, respectively. The recording poles1504A and 1504B in FIGS. 15C and 15D may be similarly shaped/configuredas those in FIGS. 15A and 15B, except that heat sinks 1502C and 1502Dsurround the recording poles 1504A, 1504B. The heat sinks 1502C, 1502Dmay have alternate outer profiles, as illustrated by dashed line 1506around heat sink 1502C. A similar outer profile could be used aroundheat sink 1502D.

In other embodiments shown in FIGS. 15E and 15F, respectively, a heatsink 1502E and/or pole material 1504F (e.g., return pole) can be coupledto NFT 1500 away from the narrow part of the NFT gap. This can becombined with other heat sink/pole arrangements, as shown in FIGS.16A-16D. In FIG. 16A, a bottom-side heat sink 1502E is combined withtop-side heat sink 1502A together with narrow pole 1504A. In FIG. 16B,wide recording pole 1504B is separated from NFT 1500 by heat sink 1502Band further combined with return pole 1504F. A similar arrangement isshown in FIG. 16C, except that bottom heat sink 1502E is placed betweenNFT 1500 and return pole 1504F. Finally, FIG. 16D shows an alternateconfiguration with a heat sink 1600 extending from the sides of the NFT1500 opposite the gap.

In any of the embodiments shown in FIGS. 15A-15F and 16A-16D, the heatsinks can be formed from a material with high thermal conductivity, suchas Au or Cu, and/or alloys of these materials. The heat sinks may alsobe formed from a material that is thermally and/or mechanically stablesuch as Cr, Ru, W, etc., which may provide a trade-off between thermalconductivity and thermal and mechanical stability. In one configuration,the outer edges of the heat sinks (e.g., perimeter 1506 shown in FIG.15C) could be lined with a heat conductive material such as Au, and thecenter could be filled with a mechanically stable/robust material suchas those mentioned above. This two-part construction may be employed ifthe illustrated cross sections are at or near the ABS.

The heat sinks may be more effective in removing heat if located at ornear the ABS. In configurations where the heat sinks are proximate theNFT gap (e.g., FIGS. 15A-15D and 16A-16C) the heat sinks may beseparated from the NFT gap by a small distance. In such a case, theconductive paths to the heat sink would be small, and convection fromthe ABS could help dissipate heat in this region. Portions of the NFTaway from the NFT gap could be made significantly thicker, and thesloped pole portions could cut down through these thickened portion.This could be used to form a heat sink about the same size as the NFT.

In reference now to FIG. 17A, a cross-sectional diagram illustrates aconfiguration of a heat sink proximate an NFT according to an exampleembodiment. Analogous components to those shown in FIG. 2 are given likereference numerals in FIG. 17A. In this figure, NFT 1700 may take on anyconfiguration previously shown and discussed. Similarly, a heat sink1704 may be located proximate the NFT 1700 in any of the configurationsshown above, including those with heat sink components between the NFT1700 and a return pole (not shown). For example the heat sink 1704 maywrap fully or partially around the recording pole 202, as indicated bydashed line 1702.

The heat sink 1702 may be made from a dielectric material, such as MgO,that has a high thermal conductivity. Such a material might not beusable all the way to the ABS 110 due to, for instance, corrosion. So adielectric material 1706 may be placed near the ABS to block theheat-sink 1704 from exposure to the ABS 110. This layer 1706 couldextend around any portions (e.g., portion 1702) where the heat sink 1704could be exposed to the ABS 110. For similar reasons, a spacer 1708 maybe placed between the recording pole 202 and heat sink 1704. This spacer1708 could extend around any portions (e.g., portion 1702) where theheat sink 1704 would directly contact the pole 202. Similaraccommodations could be made to heat sink portions near a return pole(not shown).

In reference now to FIGS. 17B-17C, a front view (e.g., taken from aplane parallel the ABS 110) of plasmonic NFT elements 1710, 1720 showsshape variations according to additional example embodiments. Theseelements 1710, 1720 include curvatures along an edge where gap-facingsurfaces 1711, 1721 intersect top surfaces 1712, 1722 of the elements1710, 1712. The top surfaces 1712, 1722 generally lie along (e.g.,substantially parallel to) one or more substrate-parallel planes and mayface a recording pole (see, e.g., FIG. 15A). In FIG. 17B, the NFTelements 1710 include a convex curvature on top surfaces 1712 of theelements 1710 proximate plasmon gap 1714. At least the portion of theelement 1710 near the gap 1714 is curved/chamfered, as indicated bynon-right angle 1716. The opposing corners may also have a non-rightangle as shown, or may include a right angle as shown by dashed line1717.

In FIG. 17C, NFT elements 1720 include a concave curvature on topsurfaces 1722 of the elements 1720 proximate a plasmon gap 1724. Anangle of curvature 1726 is indicated at least near the gap 1724, and theopposite corner may include a similar angle, or remain right angled, asindicated by dashed line 1727. These non-right, edge angles 1716, 1726may be maintained along the entire length (in the y-direction) of theelements 1710, 1720, or only be proximate the output ends (e.g., endsnear the ABS). These curvatures need not be smooth, e.g., may beapproximated using straight lines, flat surfaces, etc.

The angles 1716, 1726 near the respective NFT gaps 1714, 1724 will tendto modify the curvature of the electric field lines between the gaps, asrepresented by field lines 1718 and 1728, respectively. The gap of theNFT is orders of magnitude smaller than the wavelength of light in thewaveguide dielectric materials. At such small distances, the opticalfields may behave like electrostatic fields. Assuming there is asymmetric localized charge distribution in the metal at the corner ofthe gaps 1714, 1724 (e.g., symmetric but of opposite sign), the electricfield lines 1718, 1728 will start curving outside the gaps 1714, 1724.As the convex corner angle 1716 increases, the curvature in the fieldlines 1718 start decreasing. Conversely, as concave angle 1726increases, the curvature of electric field lines 1728 will increase. Fora right angle edge (e.g., where angles 1716 and/or 1726 are zero),curvature of the electric field will be between the curvatures of fields1718 and 1728.

These different fields 1718, 1728 may affect temperature profiles in therecording media, which in turn affects the recording transitions in themedia. By tuning the fields 1718, 1728 via angles 1716, 1726, recordingtransition curvatures can be altered so as to increase the linearrecording density. The intensity of the electric field willapproximately manifest itself as the temperature in the recordingmedium. Thus the recording transitions can be altered to increase therecording density. An example of how the angle of curvatures can affecttemperature profiles is shown in the analysis depicted in FIGS. 18A-18C.

In FIGS. 18A and 18B, graphs illustrated analytical models used topredict temperature profiles in a recording media. In FIG. 18A, NFTportions 1800 (here modeled as gold, although other materials may beused such as Ag, Cu) have a 90-degree corner near the gap. The goldportions 1800 are surrounded by gap material 1802 and topcladding/dielectric material 1804. In FIG. 18B, NFT portions 1810 (alsomodeled as gold) have an angled/rounded profile (e.g., approximately 45degrees) near the gap, and are surrounded by similar gap and claddingmaterials 1802, 1804 as described for FIG. 18A. The graph of FIG. 18Crepresents expected temperature profiles in a recording material basedon these two different configurations 1800, 1810.

In FIG. 18C, the dashed and sold lines represent isotherms of theoptical spots created in a media using variations 1800 and 1810,respectively. Each of the isotherm contours represent (from smallest tolargest) temperatures of 75%, 50% and 25% of peak. The solid-linecontours (corresponding to variation 1810) are smaller in the down-trackdirection than the dashed-line contours (corresponding to variation1800). Another aspect of the variation 1810 is that there may be a dropin the NFT temperature due to the larger surface area available for heatdissipation from the gap, compared to variation 1800.

The foregoing description of the example embodiments has been presentedfor the purposes of illustration and description. It is not intended tobe exhaustive or to limit the inventive concepts to the precise formdisclosed. Many modifications and variations are possible in light ofthe above teaching. Any or all features of the disclosed embodiments canbe applied individually or in any combination are not meant to belimiting, but purely illustrative. It is intended that the scope of theinvention be limited not with this detailed description, but ratherdetermined by the claims appended hereto.

What is claimed is:
 1. An apparatus comprising: a waveguide configuredto deliver light to a transducer region; a plasmonic transducer thatincludes at least one metal plate element having an input end disposedproximate the transducer region; a recording pole proximate theplasmonic transducer at the air-bearing surface; a heat sink between theplasmonic transducer and the recording pole, surrounding at least threesides of the recording pole, and extending along at least one side ofthe recording pole that does not face the plasmonic transducer; and anair-bearing surface disposed at an angle to the substrate-parallelplane, wherein an output end of the at least one metal plate element isdisposed proximate the air-bearing surface, wherein the plasmonictransducer is configured to provide a surface plasmon-enhancednear-field radiation pattern proximate the output end in response to thelight received at the transducer region.
 2. The apparatus of claim 1,wherein the plasmonic transducer comprises a second metal plate elementseparated from the first metal plate element by a gap.
 3. The apparatusof claim 1, wherein the recording pole is tapered towards theair-bearing surface.
 4. The apparatus of claim 1, wherein the heat sinkis formed of a heat sink material that is more mechanically robust thana plasmonic material used to form the plasmonic transducer.
 5. Theapparatus of claim 4, wherein the heat sink material comprises at leastone of Cr, Ru, and W.
 6. The apparatus of claim 1, wherein a portion ofthe heat sink is disposed between the plasmonic transducer and therecording pole.
 7. The apparatus of claim 1, further comprising a returnpole disposed proximate the plasmonic transducer opposite the recordingpole, wherein the plasmonic transducer is thermally coupled to thereturn pole.
 8. The apparatus of claim 7, further comprising a secondheat sink between the return pole and the plasmonic transducer.
 9. Theapparatus of claim 1, further comprising a second heat sink proximate asurface of the plasmonic transducer that is opposite the recording pole.10. An apparatus comprising: a waveguide configured to deliver light toa transducer region; a plasmonic transducer that includes at least onemetal plate element having an input end disposed proximate thetransducer region; a recording pole proximate the plasmonic transducerat the air-bearing surface; a return pole disposed proximate theplasmonic transducer opposite the recording pole; a heat sink betweenthe plasmonic transducer and the return pole; and an air-bearing surfacedisposed at an angle to the substrate-parallel plane, wherein an outputend of the at least one metal plate element is disposed proximate theair-bearing surface, wherein the plasmonic transducer is configured toprovide a surface plasmon-enhanced near-field radiation patternproximate the output end in response to the light received at thetransducer region.
 11. The apparatus of claim 10, wherein the plasmonictransducer comprises a second metal plate element separated from thefirst metal plate element by a gap.
 12. The apparatus of claim 10,wherein the recording pole is tapered towards the air-bearing surface.13. The apparatus of claim 10, wherein the heat sink is formed of a heatsink material that is more mechanically robust than a plasmonic materialused to form the plasmonic transducer.
 14. The apparatus of claim 13,wherein the heat sink material comprises at least one of Cr, Ru, and W.15. The apparatus of claim 10, further comprising a second heat sinkbetween the recording pole and the plasmonic transducer.
 16. Anapparatus comprising: a waveguide configured to deliver light to atransducer region; a plasmonic transducer that includes at least onemetal plate element having an input end disposed proximate thetransducer region; a recording pole proximate the plasmonic transducerat the air-bearing surface; a return pole disposed proximate theplasmonic transducer opposite the recording pole and thermally coupledto the plasmonic transducer; a heat sink between the plasmonictransducer and the recording pole; and an air-bearing surface disposedat an angle to the substrate-parallel plane, wherein an output end ofthe at least one metal plate element is disposed proximate theair-bearing surface, wherein the plasmonic transducer is configured toprovide a surface plasmon-enhanced near-field radiation patternproximate the output end in response to the light received at thetransducer region.
 17. The apparatus of claim 16, wherein the plasmonictransducer comprises a second metal plate element separated from thefirst metal plate element by a gap.
 18. The apparatus of claim 16,wherein the heat sink is formed of a heat sink material that is moremechanically robust that a plasmonic material used to form the plasmonictransducer.